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SUMMARY:Peeling adhesive tape: A case study for understanding the effectiv
 e properties of heterogenous materials - Professor Kaushik Bhattacharya\, 
 California Institute of Technology
DTSTART:20130315T140000Z
DTEND:20130315T150000Z
UID:TALK43781@talks.cam.ac.uk
CONTACT:Ms Helen Gardner
DESCRIPTION:While there is a good understanding of the overall behavior of
  heterogeneous materials concerning properties that are characterized by a
  variational principle\, much remains unknown concerning those properties 
 that are characterized by evolutionary processes.  This talk will discuss 
 the simple process of peeling an adhesive tape from a rigid substrate as a
  case study to demonstrate the complexities that can arise in this situati
 on.  Specifically\, we show that that one can dramatically enhance the ove
 rall adhesive strength by patterning the elastic modulus of the tape\, and
  induce asymmetry where the force needed to peel the membrane depends not 
 only on the direction but also the sense of the peel.   Remarkably\, these
  modifications in peeling strength come from variations in the energy asso
 ciated with bending of the tape near the peeling front which is negligible
  compared to the overall energy in the system.  This illustrates that in e
 volutionary processes\, perturbations with apparently negligible energy ca
 n have an anomalously large macroscopic effect.   The talk will conclude w
 ith broader lessons for other phenomena including fracture\, dislocations\
 , phase boundaries and wetting fronts.\n\nThis is based on joint work with
  S. Xia\, L. Ponson and G. Ravichandran
LOCATION:Cambridge University Engineering Department\, LR4
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